Sunday, 18 October 2009

Exponential growth in interest in circumcision

A little bit of fun.

The following graph shows the level of interest in circumcision (as measured by the number of PubMed abstracts published in a given year) vs time. The line shown is the best fit for the data (found using least squares regression, the curve shown is exponential, with the formula being exp(-109.44761+0.05724*y), where y is the year).

What this means is that interest in circumcision is not only increasing, but the rate of increase is itself increasing. The interesting questions are: why? And will it continue?

For those who are interested, the graph is reasonably easy, though a bit tedious, to reproduce. Go to PubMed, and search for "circumcision 1970[dp]", without including the double quote marks. Note the number of items found. Then repeat for all years from 1971 to the present. I typed the figures straight into a CSV file, which I then loaded into R for analysis and plotting.


Caroline said...

If each dot represents a year, it appears that the number of papers peaked around 06 or 07 and has been dropping steadily since then.

I agree, that generally, the rate has gone way up since 1970, but I question your use of a best fit line in this case.

It would be interesting to start the graph at 2006 and then see what happens these next few years.

Jake said...

Thanks for your comment, Caroline.

Your description is accurate: there is indeed a peak (in 2007, with 288 papers), and an apparent fall since then.

There are a total of two data points since 2007, and I suspect that both are underestimates. In the case of 2009, that's almost a certainty: two and a half months of 2009 are still to come, which is plenty of time for more publications. In the case of 2008, it's probable that there are still a few papers awaiting indexing by PubMed, though probably only a few.

For these reasons, I believe it is a mistake to pay too much attention to years later than 2007.

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